BGA components typically comprise plastic or ceramic packaged integrated circuit (IC) components in which the external contacts on the package for the IC chip on the inside is in the form of a plurality of solder bumps, typically as solder balls or as tiny columns. A common construction is a high melting temperature solder ball. The top part of the ball is soldered to the package and makes electrical contact with the chip terminals. The bottom part is used to solder the component to pads located on the surface of the PCB. To achieve proper soldering, the solder balls, of which there may be anywhere from 10-1000 arranged in rows and columns, must be heated to the melting point of the solder, often referred to in this art as the reflow or eutectic temperature of the solder, meaning the temperature that the solder must reach before it melts and can wet the solder pad. Different components often have different reflow temperatures. In soldering such components, individually, to a PCB, care must be exercised to ensure that the solder reaches the proper reflow temperature but the component is not overheated to avoid the internal chip parts or the package from being damaged.
Apparatus is available for soldering a plurality of components to a PCB, by placing the entire PCB inside an oven that is programmed to subject the entire PCB to a controlled heating cycle involving a first preheat or ramp stage to some intermediate temperature to avoid thermal shock and control flux paste evaporation, followed by a second preheat or soak stage at a higher temperature wherein the flux is activated but still at a temperature below the reflow temperature, followed by a reflow or spike stage when the temperature is quickly raised to the reflow temperature and the solder goes from the solid to the liquid stage but only for a short duration to minimize PCB or component damage, followed finally by a controlled cooling stage to well below that of the second preheat stage. Such ovens can use radiant (IR) heaters for the first and second preheat stages, to which is added forced air convection heating for the reflow stage. Heating can be carried out in air or more commonly in an inert gas such as nitrogen or forming gas.
This equipment, however, is unsuited for processing single components. A common situation is where an operator desires to solder a single component to a PCB to which other components have previously been soldered. The previously described oven cannot be used for this purpose because it would undesirably melt all the existing soldered connections without a suitable flux being present. A similar problem arises when an operator desires to desolder one component from the PCB board without affecting any other soldered components. Still another example is when an operator desires to resolder an existing soldered component if a cold solder joint is suspected.